CEG411/611 Microprocessor Based System Design What is this course about? Computer : Processor, Memory, I/O Microprocessor versus microcontroller Embedded Systems Processor I/O Memory Bus

EVB (Evaluation Board): Axiom CSM12C32 ( Chip: MC9S12C32 from Freescale (formerly, a Motorola division) –For chip documentation in PDF files, see C:\68HC12\ 9S12C32_Chip 68HC12 versus 68HCS12

Lab 1 Preparation Monitor, MON12, Monitor commands (Sec ) MD, MM, LOAD, CALL Address versus data Hexadecimal number system and Memory map C, Assembly, Machine Code ICC12 and as12 Step by step instructions S record file, list file, map file

Sample C Programs C review (Chapter 5, sample_c.c) –main( ), function call –data types (char, unsigned char, int, short, long, float) –Condition check (true, false, if, else) –for loop, while loop –putchar(), puts(), printf() tone.c : timer, output compare (Sec 8.6) switch_LED.c : simple parallel port usage

Let Y be a generic register which can be PORTA, PORTB, PORTE, PTAD, PTT, PTP, PTS, PTM, DDRA, DDRB, and so on. Contents of Y: Y 7 Y 6 Y 5 Y 4 Y 3 Y 2 Y 1 Y 0 Output (Use Y 1 as an example) –Set bits : Y |= 0x02; –Clear bits : Y &= ~0x02; or Y &= 0xFD; –Toggle bits : Y ^= 0x02; Input –Check if set : if( Y & 0x02 ) –Check if clear : if( !(Y & 0x02)) –Wait until set : while( !(Y & 0x02) ) ; –Wait until clear: while(Y & 0x02) ; Simple Parallel Port Usage

A simple parallel port usage example: switch_LED.c MC9S12C32 PB4 PE0 PP5 PA0 SW1VCCSW2VCC LED1 VCC LED2

Measuring Pulse Width Without Using Input Capture Use while loops and read TCNT to get T1, T2 If(T2 > T1) T = T2 – T1; else T = 0xffff – T1 + T2 + 1; Timer Overflow? 6812

Interrupt Programming Interrupt versus polling Interrupt programming –Write an ISR (interrupt service routine) –Register the ISR, p. 268 –Enable ISR (locally and globally) tone_interrupt.c example On EVB, pressing the reset button clears the MON12 (user) interrupt vector table contents Chapter 6

ADC (Chapter 12) ADC basics, a 2-bit ADC example, Sec , Example 12.1 Analog = V L + Digital * (V H -V L )/(2 N -1) ADC Internal: Successive Approximate Method, Sec Signal Conditioning Circuits based on OP Amp: Sec & ADC Programming: Sec –adc_scan.c

ADC Timing (ATDCTL4), p. 602 ATD Clock = Bus Clock / [2(PRS+1)] –Bus Clock : 24 MHz on EVB –PRS : bits 4 to 0 of ATDCTL4 ATD Conversion Time per Sample = [2 + 2(SMP+1) + B] ATD clock cycles –SMP : bits 6 and 5 of ATDCTL4 –B: 8 or 10 (for 8-bit and 10-bit ADC, respectively)

Assembly Programming Why assembly programming? –Understand computer/C internal operations –More efficient coding CPU Registers (Sec. 1.8) D (A:B) : accumulator; X, Y: index registers; SP : Stack Pointer; PC: Program Counter CCR : Condition Code Register S X H I N Z V C

Memory Addressing – Big-Endian versus Little-Endian – Memory Mapped I/O A sample assembly program (tonevb.asm) –Label, Opcode, Operands, Comments –Assembler directives (e.g., ORG) CPUMemory 16-bit Address 8/16-bit Data

Load/Store Instructions (Sec ) and Addressing Modes (Sec. 1.9) Examples –LDAA #$55 immediate mode –LDAA #55 immediate mode –LDD #$0F20 immediate mode –LDAA $55 direct mode –LDAA $0F20 extended mode –LDD $0F20 extended mode –LDAB 3,X indexed mode LDX, LDY, LEAS, LEAX, LEAY –LEAS -4,SP : SP ← (SP)-4 (to allocate space for local variables for subroutines) STAA, STAB, STD, STS, STX, STY

Example: int m, n; // assume m is at $3000 // assume n is at $3002 m = n + 5; LDD $3002 ADDD #5 STD $3000 How about char instead of int?

More instructions (Sec. 1.11) –Transfer (register to register) and Exchange (swap registers): TAB, TAP, TBA,....; EXG, XGDX, XGDY –Move (memory to memory): MOVB, MOVW –Add and Subtract (always involves CPU registers) Register + Register : ABA, ABX, ABY Register + Memory : ADCA, ADCB, ADDA, ADDB, ADDD Register – Register : SBA Register – Memory : SBCA, SBCB, SUBA, SUBB, SUBD

Assembler Directives (Sec. 2.3) –ORG (Origin), EQU (Equate) –Specify Constants: fcb (Form Constant Byte, or db), fcw (Form Constant Word, or dw), fcc (Form Constant Character, String), fill –Reserve Space: rmb (reserve memory byte), rmw (reserve memory word) Examples ORG $3800 array fcb $11,$22,$33,’5,25,100 buf rmb 20 msg fcc “Hello World” tmp fill $11,20

Program Loops (Sec. 2.6) –Loop constructs –Branch conditions/instructions compare (A to B, a register to a memory) or test (A, B, or a memory location) S X H I N Z V C CCR branch (BRA, BEQ, BNE, BLS,...)

Examples 2.14 (p. 68), 2.15 –Draw flowchart –Revise flowchart Example 2.17 –BRCLR oprand,mask,label branch to label if the bit(s) is (are) clear while(!(TFLG1 & 0x01)); // wait until flag is set // the above C statement is equivalent to here BRCLR $004E,$01,here Note that $004E is the address of TFLAG1 –BRSET oprand,mask,label

Subroutine Calls (Chapter 4) Stack, Stack Pointer, Push, Pull –PSHA, PSHB, PSHD, PSHX, PSHY : Decrement (SP) first, then write data –PULA, PULB, PULD, PULX, PULY : Read data first, then increase (SP) Example: Ex. 4.1 LDS #$3E00 LDAA #$3B LDD #$302F PSHA PSHD

BSR, JSR, RTS, Caller, Callee (Sec. 4.4) BSR SORT SORT RTS Parameter Passing, Result Returning, and Allocation of Local Variables (Sec. 4.5) –Using registers versus using stack

Stack Frames (Sec. 4.6), Ex. 4.3 Example C versus Assembly Local Variables Saved Registers Return Address Incoming Parameters & Return Values 1. Caller: PSHX 2. Caller: BSR 3. Callee: PSHD 4. Callee: LEAS -4,SP

void main() { int a, b; a = sum(b, 3); } int sum(int x, int y) { int s; s = x + y; return s; } LDD 5,sp *** b PSHD LDD #3 PSHD LEAS -2,sp *** result JSR Sum.... Sum: PSH... *** save reg LEAS -2,sp *** s......

More Timer Functions Timer Overflow (p. 367): TSCR2 bit 7 (TOI), TFLAG2 bit 7(TOF) Input Capture (Sec. 8.5) and Examples Real-Time Interrupt (Sec. 6.7): CRGINT bit 7 (RTIE), CRGFLG bit 7 (RTIF) n = RTICTL bits 6-4; m = RTICTL bits 3-0 OSCCLK (16MHz on EVB)/[(m+1)2 (n+9) ] Pulse Accumulator (Sec. 8.7): a 16-bit counter Pulse Width Modulation (PWM) (Sec. 8.10)

Parallel Ports, I/O Synchronization and Handshaking (Sec. 7.4) –Strobe vs. Handshake –Input/Output Handshaking Protocols Serial Interface (Chap. 9 & 10): –SCI vs. SPI –SCI: RS-232, Start-bit, Stop-bit, Parity –SPI (p.482): SCK, SS, MISO, MOSI –Other Serial Interface Protocols: USB, PCI Express, SATA, Ethernet